Step stool



FIG. 1 is a front perspective view of a design for a step stool;

FIG. 2 is a rear perspective view of the design as seen in FIG. 1;

FIG. 3 is a left side elevational view of the design as seen in FIG. 1;

FIG. 4 is a right side elevational view of the design as seen in FIG. 1;

FIG. 5 is a top plan view of the design as seen in FIG. 1;

FIG. 6 is a bottom plan view of the design as seen in FIG. 1;

FIG. 7 is a front elevational view of the design as seen in FIG. 1; and,

FIG. 8 is a rear elevational view of the design as seen in FIG. 1.

The broken lines shown in the figures are for the purpose of illustrating portions of the step stool that form no part of the claimed design. 

CLAIM The ornamental design for a step stool, as shown and described. 